Ecotone Dynamics and Boundary Determination in the Great Dismal Swamp

Data on hydrogeology, soils, and vegetation collected on four transects across the 48-km wetland-to-upland transition zone of the Great Dismal Swamp of Virginia/ North Carolina, USA, were used to analyze changes along the moisture/elevation gradient, to characterize the wetland-upland ecotone, and to select tentative wetland-upland bound- aries based on these three parameters. Transition zone vegetation was dominated by three facultative hydrophytes: Acer rubrum, Liquidambar styraciflua, and Nyssa sylvatica. On the basis of ordination performed on consecutive 25-m transect increments, each transect was divided into three zones: wetland, ecotone, and upland. The water table was within the root zone (0-30 cm below the ground surface) an average of 25-100% of the growing season at all well sites in wetland, 100 m horizontal distance and 0.4 m vertical distance. Only a vegetation boundary was established on the fourth transect.